1. Field of the Invention
The invention generally relates to an optical microscope and, in particular, a stereoscopic, long-distance microscope having a target in the range of 100 mm-300 mm from the front optical element of the microscope.
2. Description of Related Art
The prior art includes a significant number of telescopes and the like that have the following basic structure: a convex front lens; a concave rear mirror for receiving light from the front lens; a secondary mirror located on the backside of the front lens for receiving light focused from the rear mirror; an angled mirror, or the like, for receiving reflected light from the secondary mirror; and, an eyepiece for viewing the image reflected from the angled mirror. The target is typically located at a substantial distance from the front lens and the front lens and rear mirror have substantially the same diameter. An example of a well known telescope for observing astronomical events or observing or photographing terrestrial events, is the Questar 31/2 sold by the Questar Corporation, 6204 Ingham Road, New Hope, Pa., 18938.
Other optical devices which include a compound refractive first front lens, a concave primary rear mirror, a secondary mirror and a mechanism for focusing the result onto an eyepiece are found in the following patent disclosures: U.S. Pat. Nos. 2,748,658; 2,726,574; 3,532,410; and, 5,471,346.
U.S. Pat. Nos. 4,755,031 and 5,181,145 describe similar structures. In particular, U.S. Pat. No. 5,181,145 discloses a beam that is reflected from a secondary, convex mirror which impinges on a beam splitter thereby producing two images at two different points. U.S. Pat. No. 4,835,380 also describes the use of a beam splitter at the output end of a similar structure.
The following patents disclose related structures, but without a compound refractive lens at the front end: U.S. Pat. Nos. 2,753,760; 3,411,852; 3,468,597; 5,159,495; and, 5,161,051.
While the foregoing prior art disclosures have some nominal similarity to the present invention, nevertheless, none of them appear to describe a structure or use which permits the device to be used as a stereoscopic, long-distance microscope. Such a device can be especially useful for unique applications such as neuro-surgery, high-speed material processing and the inspection of complex materials for flaws and irregularities.
It was in the context of the foregoing need that the present invention arose.